1. Field of the Invention
The present invention relates to a machine tool, and particularly to a machine tool with a function to automatically modify cutting conditions.
2. Description of the Related Art
In executing a cutting process on a workpiece using a machine tool, in some cases the tool rotational speed and cutting feed speed stored in a machining program need to be corrected in order to modify the cutting conditions according to the situation. In a complicated machining program, however, the tool rotational speeds and cutting feed speeds are usually designated individually in a large number of locations, and it is extremely troublesome to correct all the cutting conditions manually. It is also extremely difficult to determine whether the modified cutting conditions are appropriate or not or whether the cutting conditions including the cutting load are within an appropriate range or not. Japanese Patent Application Laid-Open No. 2000-084794 and Japanese Patent Application Laid-Open No. 2007-94458 disclose techniques for automatically modifying the cutting conditions.
The technique disclosed in Japanese Patent Application Laid-Open No. 2000-084794 aims to automatically modify the cutting conditions to optimum cutting conditions but does not take into consideration intentional automatic modification of the cutting conditions within an appropriate range. This technique, therefore, is not capable of responding to requests such as “wishing to lower the current cutting conditions a little bit more to increase the life of the tool, although the current cutting conditions are not particularly problematic.”
The technique disclosed in Japanese Patent Application Laid-Open No. 2007-94458, on the other hand, is capable of solving the problem described above, but cannot determine whether the modified cutting conditions are appropriate or not. Moreover, this technique merely takes the cutting feed speeds into consideration and is not capable of modifying the cutting conditions in response to the rotational speed of the spindle or the actual cutting load.
The conditions upon cutting, such as the number of tool revolutions and the cutting feed speeds, are usually designated specifically within the machining program and therefore can be modified relatively easily both manually and automatically. The cutting widths and cutting depths, on the other hand, are usually not designated specifically in the machining program. Therefore, in order to modify these cutting conditions, the machining program needs to be corrected by manually inputting the cutting conditions, while comparing the shape of the machined object with the machining program, bringing about a problem that modifying these cutting conditions cannot be performed easily.